Color displays are used in a variety of electronic devices. These include monitors for personal computers, televisions, and other video displays. These displays may be cathode-ray tube devices, or projection devices.
One type of projection device is based on the optical properties of liquid crystals, such as nematic crystals. These projection devices often include a layer of liquid crystal disposed over a semiconductor transistor array. Often, the array is one of complementary metal-oxide-semiconductor (CMOS) transistors that are used to selectively produce electric fields across the layer of liquid crystal. These electric fields change the polarization angle of the liquid crystal material molecules enabling the modulation of light that traverses this material. The light may be reflected by reflective elements or may be transmitted to the screen. In either case, the modulated light is projected onto a screen by optical elements forming a video image. In case of reflection, projection devices are referred to as liquid crystal on silicon (LCOS) projection displays.
Some factors that impact image quality of displays are resolution, brightness, contrast, and color depth. Resolution is the number of pixels a screen displays. Often, the resolution is expressed in a particular pixel dimension (e.g. 800×600 for many computer monitors). In this example, the monitor has 800 pixels in the horizontal dimension, and 600 pixels in the vertical dimension. Of course, the greater the number of pixels for a given display area, the smaller area of each pixel, and the greater the resolution.
Color depth defines how many colors can be displayed on a screen. Generally, color depth is described in binary logic (bits). Each of the three primary colors used in color displays (red, blue, green) has a number of bits that describes its color depth, or the number of shades of a particular color that may be displayed. The number of colors is normally described via binary exponential notation (e.g., 28 (referred to as 8 bit video) for 256 shades of each of the three primary colors). As can be readily appreciated, the greater the number of color bits, the greater the number of shades of the color, and the greater the color depth. Of course, the greater the color depth, the better is the display quality.
While the resolution, brightness, contrast, and color depth may be chosen for a particular desired image quality, certain factors may deteriorate the image quality. For example, differences in both the optical path and the imager characteristics in LCOS projection devices can have deleterious effects on the quality of the projected image.
As it is useful to correct imaging errors in displays, a number of methods have been devised. One such method includes evaluating the brightness distributions individually for a set of video levels for each color path. However, not all of these picture elements are stored in memory for practical reasons.
What is needed is a correction method and apparatus, which overcomes certain drawbacks of known correction schemes.
In accordance with an exemplary embodiment of the present invention, a method of correcting a video signal comprises retrieving a correction data from a respective one of a plurality of memory devices; reordering the correction data to a predetermined order for a particular segment; and interpolating a plurality of correction data so that all pixels in said particular segment has a corresponding one of said correction data.
In accordance with another exemplary embodiment of the present invention, apparatus for correcting video comprises a plurality of memory devices, each having a plurality of correction data; a cross-bar switch, which reorders at least some of said plurality of correction data to a predetermined order for a particular segment; and an interpolator which calculates a plurality of interpolated correction data, wherein one of the correction data corresponds to one of a plurality of pixels in the segment.